This invention relates to novel 2,7-di(arylamino)fluorenes which are further substituted at the 9-position with one or more crosslinkable moieties and methods for the preparation of such compounds. The invention further relates to oligomers and polymers of such substituted fluorene compounds as well as films and coatings prepared from such compounds, oligomers, polymers, and blends thereof, processes for preparing such films and coatings, and electronic devices, especially electroluminescent devices comprised of one or more layers of such polymer films.
Polymers and oligomers of fluorenes substituted by alkyl groups at the 9-carbon position have been reported by Fukuda et al. in Japanese Journal of Applied Physics, Vol. 28, pp. L1433-L1435 (1989). Such polymers are disclosed as useful a luminescent materials in the preparation of light-emitting diodes. These polymers were prepared by the Kovacic procedure wherein the appropriate fluorene monomers were treated for several days with a large excess of oxidizing metal salts such as ferric chloride. The structures are represented as poly(fluorene-2,7′-diyl)s. A series of patents including U.S. Pat. Nos. 6,605,373, 6,362,310, 6,255,449, 6,255,447, 6,169,163, and 5,962,631 disclosed certain 2,7-disubstituted fluorene compounds further substituted at the 9 position with 1 or 2 substituents including C1-20 hydrocarbyl groups or C1-20 hydrocarbyl groups containing one or more S, N, O, P or Si atoms, C4-16 hydrocarbyl carbonyloxy groups, C4-16 aryl(trialkylsiloxy) groups, and alkylidenyl or divalent spirocycle forming groups such as 5-norborn-2-enylidenyl groups. Suitable substituents at the 2 and 7 positions included crosslinkable groups. An improved synthesis of such compounds was also disclosed in U.S. Pat. No. 5,777,070.
In JP 20-327640 certain 2-(diarylamino)-7-di(arylamino)aminofluorene derivatives were disclosed for use as hole transport materials in organic electroluminescent devices. Similar uses were disclosed for additional diarylaminofluorene derivatives in JP 09-258465. In JP 11-322679 the preparation of certain bisarylaminofluorenes was disclosed. In EP-A-823,669 a series of fluorene derivatives, including bis(diarylamino)fluorene compounds for use as photosensitive layer materials for organic light emitting diodes (OLEDs) were disclosed.
Macromol. Rapid Commun. 20, 224-228 (1999) and Macromol. Rapid Commun. 21, 583-589 (2000) describe certain crosslinkable triarylamine hole-transport materials suitable for use in preparation of multilayer organic light emitting devices by solution spin-coating techniques. J. Phys. Org. Chem. 16, 194-201 (2003), Polymer Preprints 43 (1), 104 (2002) and Polymer Preprints 44(1), 1061 (2003) elucidate the structure and electroluminescent properties of 9,9-didecyl-2,7-bis(N,N-diphenylamino)fluorene.
Recent advances in display technology have resulted in improved compounds and fabrication techniques for electroluminescent devices such as light-emitting diodes (LED's). High luminance materials are now available for a large portion of the visible light spectrum, including blue light emitting compounds. Recently it has been discovered that improved lifetimes and efficiencies of the active or light emitting layer of a multilayer LED can be obtained by incorporation of a charge transport layer into a multilayer LED between the active or light emitting layer and the anode. Such layers may also be referred to as a hole injection and/or hole transport layer where the purpose is to improve hole injection into the light emitting layer and to provide a buffer layer between the anode and the light emitting layer. In other applications, the inter-layer may act as an electron blocking layer to balance charge carriers for optimization of device efficiency and lifetime.
The present invention is directed to novel compounds for use in such interlayers of a multilayer LED, as well as in other electronic devices such as field effect transistors (FET's), photovoltaic cells, and even for integrated circuits or printed circuit boards.